Isomer molecules


Two molecules are isomers if 1) they are neither superimposable, nor conformers 2) they have the same molecular formula


Two molecules are constitutional (structural) isomers if 1) they are isomers 2) they have a different semi-developed formula


Two molecules are configurational (stereo) isomers if 1) they are isomers 2) they have the same semi-developed formula


Constitutional (structural) isomerism

Different ramification of the hydrocarbon chain:

- Chain isomerism -

Different position of a functional group:

- Position isomerism -

Different function:

- Function isomerism -

Configurational (stereo) isomerism

Rigidity of the C=C double bond:

- Cis-trans (E,Z or geometrical) isomerism -

Atom C with 4 different substituants (asymetrical C , C*):

- Enantiomerism -

Same substance or no?

The isomers can be separated at normal temperature.

Two isomer molecules do not belong to the same chemical substance.